Abrasive belt device

ABSTRACT

A method and means for incorporation into abrasive belt grinding equipment to extend the life of abrasive belts by regulating the belt breakdown rate for optimum operating life and by aiding in the removal of grinding swarf or other dulling and filling components from the abrasive surface while the abrasive belt performs its production operation.

United States Patent Inventor Appl. No.

Filed Patented Assignee Randall S. Manchester Troy, N.Y.

Nov. 29, 1968 Mar. 23, 197 1 Norton Company Troy, N.Y.

ABRASIVE BELT-DEV ICE 5 Claims, 3. Drawing Figs.

US. Cl Int. Cl Field of Search ReferencesCited UNITED STATES PATENTS E 2,646,654 7/1953 Brink .L 5llll35 Primary Examiner-Othell M. Simpson Attorney-Hugh E. Smith ABSTRACT: A method and means for incorporation into abrasive belt grinding equipment to extend the life of abrasive belts by regulating the belt breakdown rate for optimum operating life and by aiding in the removal of grinding swarf or other dulling and filling components from the abrasive surface while the abrasive belt performs its production operation.

PATENIEU HAR23197| l VE TOR RA-0ALL ANCHESTER 91% ATTONEY ABRASIVE BELT DEVICE BACKGROUND OF INVENTION In the manufacture of coatedabrasives for fabrication into belts, one of the required operations is flexing the material from which the belt is to be fabricated to avoid random major cracks in the adhesive coatings on the belt when handling or initially running the finished belt over the drive pulleys, etc., of the device on which it is being mounted for use. Flexing can be defined as the imparting to the adhesive coatings of a coated abrasive material of a plurality of controlled cracks in effect forming areas of weakness in the structure permitting it to bend or fold in a manner determined by the type, location and number of the controlled flex cracks. The degree of flex given to the material will vary depending upon the product and the average end use requirement. US. Pat. No. 1,647,475, for example, illustrates a double 90 bar flex while U.S. Pat. No. 3,133,801 shows a much more complete or random flex.

The degree of flex is limited due to the fact that overflexing results in serious degradation of the adhesive bond between the abrasive grain and the backing and severely limits the life of the belt. Failure in such instances is usually due to rapid shedding of the abrasive grain. However, as the belt wears the need exists for the abrasive grain to shed in order to cause fresh abrasive grains to be brought into operation. Any standard flex is usually greater than needed for a new abrasive belt and is yet not sufficient to permit a worn belt to properly break down. In other words, the flex requirement for optimum performance of a belt is not constant throughout the life of a belt but varies from a minimum with a new belt to a maximum with a dulled, worn belt.

Efl'orts have been made in the past to provide means for correcting this problem. For example, US. Pat. No. 2,646,654 provides a studded roller adapted to engage the back surface of an abrasive belt in conjunction with a resilient backup roller which engages the face or abrasive side of such belt. While partially effective, the spaced studs on this device give an uneven and varying flex to the belt and the associated roller on the face side is subjected to rapid wear due to the abrasive action of the belt on its surface. The present invention represents an improvement over devices of this type.

SUMMARY The present invention provides a method and means for varying the flex throughout the operational life of the belt. This can be done manually or preferably automatically as described below. In general, the method consists of either continuously and gradually increasing the flex of the belt on the machine which carries the belt during its grinding life or intermittently flexing the belt in increasingly more severe steps as the belt wears in use by the application of a uniform disruptive force in a narrow zone across the entire width of the belt. The means generally is a metal strip having a rounded edge or a small diameter bar or similar structure at least as wide as the belt which is so positioned as to be adjustably applied against the back only of the abrasive belt while it is on the grinding machine. In passing over this flex means, which applies a uniform disruptive force on the back of the belt, the coated side of the belt, under tension, develops additional cracks in the adhesive costing.

IN THE DRAWINGS FIG. 1 is a schematic flow diagram of the method as applied to an automatic system.

' FIG. 2 is a diagrammatic illustration of another type of flexing means which can be employed.

FIG. 3 is a diagrammatic illustration of a third type of flexing means useful in this invention.

Referring now to FIG. I, the abrasive belt is driven by a contact roll 11 operated by motor 9. The power required to drive roll 11 is a measure of the grinding force involved and as the cutting ability of the belt decreases this power requirement gradually changes. Ammeter I2 is hooked into the motor 9 and measures this changing power requirement.

The belt 10 travels over idler roll 13 and an adjustable idler pulley 14. The flex unit 15 consists of a continuous flex bar I6 at least as wide as the belt 10 and capable of movement towards and away from the back of the belt 10, as indicated by the arrows A. This movement can be produced by any suitable power source such as air, hydraulic piston, mechanical screw or the like and the power source is shown generally at 17. Connecting ammeter 12 to power source I7 are suitable electrical leads l8 and 18' which pass through microswitches l9 and 19. As the power requirement of roll 11 changes, due to wearing down of the grain against workpiece 20, microswitch 19 opens and energizes power source 17. This causes flex bar 16 to move into contact with the back of belt 10 and to further flex the belt causing the adhesive to increase its grain shedding rate. As the grain sheds and new grains contact the workpiece, the power requirement again returns to normal, microswitch 19 closes, and switch 19 opens causing power source 17 to reverse the direction of movement of flex bar 16 and to pull such bar away from belt 10. This action is repeated automatically throughout the life of belt 10. Idler pulley I4 is pivotable to follow the belt as it is extended by flex bar 16 and the extend of such pivotable movement is shown by the dotted lines which also show the position of the flex bar I6 and belt l0 under the maximum flex conditions. Obviously, power source 17 and flex bar 16 can be programmed for intermittent contact with belt 10 or bar 16 can be manually moved against belt I0 when and as flex is required.

FIG. 2 illustrates another type of unit which provides greater wrap of the flex bar and which can be automated in the same manner as that of FIG. 1. Here the idler roll 30, carrying abrasive belt 31, is modified to mount the flex means of the present invention. Idler pulleys 32 and 33 support the belt 31 (driven in the direction of the arrows by a driven contact roll not illustrated) beyond main idler roll 30 and provide space in which flex bar 34 can move. Bar 34 is shown in maximum flex position and is retractable as shown by arrows B into the dotted line position where no flex is being applied to belt 31.

FIG. 3 is quite similar to FIG. 2 except that here the idler pulleys have been replaced by guide shoes or platens 42 and 43 mounted behind idler roll 40. Abrasive belt 41 is shown passing over these platens 42 and 43 in the nonflex position with flex bar 44 retracted to inoperative position. This bar 44 can be moved into the dotted line position when flex is to be applied.

Variations of the actual flex bar are many. It may be a sharp-edged rectangular bar, a round rod, a metal angle iron, etc., and may vary in thickness depending upon the type and severity of flex required. Likewise, the degree of travel of the bar, while limited in its maximum by the stretchability of the belt, can be varied to minimize or maximize stretch as desired. The flex means must, however, be uniform as regards the portion thereof which contacts the back of the abrasive belt and must extend across the entire width of such belt.

An additional advantage has been found with this device, namely, the dislodgement of swarf or entrapped material from among the abrasive grains of the belt surface. This helps to keep the belt free-cutting and contributes to the extension of its useful life.

The positioning of the means of the present invention will vary depending upon the grinding machine machine with which it is used. It may be interposed in a portion of the unit which comprises mounting a coated abrasive belt on a grinding machine in operative contact with a workpiece; moving said belt against said workpiece whereby the abrasive surface of said belt is dulled; and applying a disruptive force uniformly across the entire width of the belt in a narrow zone against the back of said dulled belt while it is operating in said machine to increase the amount of flex of such belt and to increase the shedding rate of the dulled abrasive grains.

2. A method as in claim 1 wherein the application of such disruptive force is repeated a plurality of times during the grinding life of said abrasive belt.

3. A method as in claim 1 wherein the disruptive force is applied automatically as the result of changes in power demand for driving said belt against the workpiece.

4. A device for increasing the operative life of coated abrasive belts which comprises: 

1. A method for improving the life of coated abrasive belts which comprises mounting a coated abrasive belt on a grinding machine in operative contact with a workpiece; moving said belt against said workpiece whereby the abrasive surface of said belt is dulled; and applying a disruptive force uniformly across the entire width of the belt in a narrow zone against the back of said dulled belt while it is operating in said machine to increase the amount of flex of such belt and to increase the shedding rate of the dulled abrasive grains.
 2. A method as in claim 1 wherein the application of such disruptive force is repeated a plurality of times during the grinding life of said abrasive belt.
 3. A method as in claim 1 wherein the disruptive force is applied automatically as the result of changes in power demand for driving said belt against the workpiece.
 4. A device for increasing the operative life of coated abrasive belts which comprises: A. means to support and drive a coated abrasive belt against a workpiece; and B. means to periodically apply a uniform disruptive force in a narrow zone against the back and across the entire width of said abrasive belt while it is being driven on said first-mentioned means.
 5. A device as in claim 4 wherein additional means are provided to measure the power demand to drive said first-mentioned means and upon a change in such power demand to actuate said second-mentioned means. 